Maxim Integrated MAXQ Family - Manual (Page 89)

9-11
MAXQ Family User’s Guide
9.3.2 Measure High-Pulse Duration Repeatedly
To measure the duration of high pulses seen on the T2P input pin repeatedly, Timer 2 could be configured for a single-shot delayed
run, gating enabled for logic low, capture on the falling edge. The CPRL2 bit could be set to generate a reload on each falling edge.
; ------------------ Reset State: T2R = T2V = T2C = 0000h ------------------------
MOVE T2CFG, #00000100b ; T2CI =0 (sysclk/N input)
; T2DIV[2:0] =000 (/1)
; T2MD =0 (16-bit)
; CCF[1:0] =10 (falling edge)
; C/T2 =0 (timer/capture)
MOVE T2CNA, #10001111b ; ET2 =1 (enable Timer 2 ints)
; T2OE[0] =0 (input)
; T2POL[0] =0 (gating level = ‘0’)
; TR2L:TR2 =01 (start timer 2 on single shot condition)
; CPRL2 =1 (reload on capture edge)
; SS2 =1 (single-shot mode)
; G2EN =1 (gating enabled)
; ------------------ TCC2 Interrupt : DURATION = T2C
EVENTS:
1A: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE BEGINS; TIMER CLOCK GATED SINCE T2P PIN = 0.
2A: GATING CONDITION REMOVED; TIMER RUNS.
3A: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE ENDS; DURATION = T2C. TIMER CONTINUES TO OPERATE
SINCE TR2 = 1, BUT TIMER CLOCK GATED SINCE T2P PIN = 0.
4A: GATING CONDITION REMOVED; TIMER RUNS.
1B: GATING CONDITION REMOVED; SINGLE-SHOT CAPTURE CYCLE BEGINS.
2B: FALLING EDGE CAUSES CAPTURE/RELOAD; SINGLE-SHOT CAPTURE CYCLE ENDS; DURATION = T2C. TIMER CONTINUES TO OPERATE
SINCE TR2 = 1, BUT TIMER CLOCK GATED SINCE T2P PIN = 0.
3B: GATING CONDITION REMOVED; TIMER RUNS.
T2P PIN
CODE EXECUTION:
POINT A
CODE EXECUTION:
POINT B
1A 2A
1B 2B 3B
3A 4A
Figure 9-5. Timer 2 Application Example—Measure High Pulse Width
Maxim Integrated